Characterization of Molybdenum-Free Nitrate Reductase from Haloalkalophilic Bacterium Halomonas sp. Strain AGJ 1-3

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A. N. Antipov^1*, E. V. Morozkina¹, D. Yu. Sorokin², L. I. Golubeva¹, R. A. Zvyagilskaya¹, and N. P. L'vov¹

¹Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, 119071 Moscow, Russia; fax: (7-095) 954-2732; E-mail: a_antipov@hotbox.ru

²Institute of Microbiology, Russian Academy of Sciences, pr. 60-letiya Oktyabrya 7/2, 117811 Moscow, Russia; fax: (7-095) 135-6530; E-mail: soroc@inmi.host.ru

^* To whom correspondence should be addressed.

Received July 2, 2004; Revision received July 13, 2004

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Nitrate reductase from the haloalkalophilic denitrifying bacterium Halomonas sp. strain AGJ 1-3 was isolated and purified to homogeneity. The isolated enzyme belongs to a novel family of molybdenum-free nitrate reductases. It presents as a 130-140 kD monomeric protein with specific activity of 250 µmol/min per mg protein. The enzyme reduces not only nitrate, but also other anions, thus showing polyoxoanion reductase activity. Enzyme activity was maximal at pH 7.0 and 70-80°C.

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KEY WORDS: Halomonas sp., nitrate reductase, denitrification, alkalophiles, soda lakes

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